Firearm extraction mechanisms, particularly for semi-automatic firearms, often rely on a somewhat tenuous arrangement for securing a shell casing to a bolt of the firearm. The uncertainties associated with manufacturing tolerances of cartridges, as well as the spurious nature of the frictional forces exerted thereon, leads to instability during the extraction process that can cause failures to eject and sporadic ejection patterns. This can particularly be a problem when handling smaller diameter casings that are generally associated with rimfire cartridges (i.e., cartridges that are fired by impingement of a firing pin near the periphery of the base of the cartridge), particularly higher powered rimfire cartridges.
Also, the instability of traditional extractor mechanisms is more problematic when the retracting bolt speed is variable. Where the bolt is moved too slowly the cartridge case can become instable long before it's delivered to the ejector.
An ejector mechanism that overcomes these problems would be welcomed.